Ultrafast lasers have been applied to optical data processing, data transmission, optical detection having high timing resolution, and material processing. Current ultrafast laser generating mechanisms may include three types: active mode-locked, passive mode-locked and gain switched.
Regarding the active mode-locked mechanism, a suitable loss modulation component, such as an electro-optical modulation component or an acousto-optical modulation component, is placed in a resonance cavity so that a modulated frequency is equal to a longitudinal mode frequency.
Regarding the passive mode-locked mechanism, a saturation absorber is placed in a laser resonance cavity such that an inherent property, i.e., interaction between the saturation absorber and laser may be utilized without using any extra modulation source.
As to the gain switched mechanism, it allows laser to release pulsed light having high power pulses. Thus, the laser triggered by the gain switched mechanism has a greater power than that triggered by a continuous wave.